The influence of geomagnetic activity on mesospheric summer echoes in middle and polar latitudes

Abstract

Abstract. The dependence of mesospheric VHF radar echoes during summer months on geomagnetic activity has been investigated with observation data of the OSWIN radar in Kühlungsborn (54 • N) and of the ALWIN radar in Andenes (69 • N). Using daily mean values of VHF radar echoes and of geomagnetic activity indices in superimposed epoch analyses, the comparison of both data sets shows in general stronger radar echoes on the day of the maximum geomagnetic activity, the maximum value one day after the geomagnetic disturbance, and enhanced radar echoes also on the following 2-3 days. This phenomenon is observed at middle and polar latitudes and can be explained by precipitating particle fluxes during the ionospheric post storm effect. At polar latitudes, the radar echoes decrease however during and one day after very strong geomagnetic disturbances. The possible reason of this surprising effect is discussed.

Long-term changes of (polar) mesosphere summer echoes

“…Effects of photodissociation on the water vapour cannot be expected. There are some indications that there is only a small temperature effect due to increasing particle fluxes (Bremer et al, 2006;Zeller and Bremer, 2009).…”

Mesosphere summer echoes, temperature, and meridional wind variations at mid- and polar latitudes

“…Here the temperature is clearly below the frost point, so temperature variations caused by the meridional wind have lead to temperatures that still do not exceed the frost point. Here, other impacts like geomagnetic activity and ionization variations affect the PMSE variability (e.g., Bremer et al, 2006;Zeller and Bremer, 2009). Only in 2002 there is a significant impact of the meridional wind variations due to a higher mean temperature level caused by circulation anomalies.…”

Long‐term changes of polar mesosphere summer echoes at 69°N

“…Effects of photodissociation on the mesospheric water vapor cannot be expected. Moreover, there are some indications that also the influence of precipitating particle fluxes on the mesospheric temperature is only small [ Zeller and Bremer , ].…”